1. Field of the Invention
The present invention relates generally to a magnetic recording and regenerating unit for photographic film and a camera, and more particularly to a magnetic recording and regenerating unit which records magnetic information in a magnetic recording layer on the photographic film and regenerates the magnetic information recorded in the magnetic recording layer, and a camera which the magnetic recording and regenerating unit applies to.
2. Description of Related Art
Advanced photographic film has been proposed in which one side of silver salt film is coated with a magnetic layer (U.S. Pat. No. 5,130,745). A film cartridge which contains the film and a camera which uses the film cartridge for photographing have also been proposed, and they are standardized worldwide.
As shown in FIGS. 32(a) and (b), an advanced cartridge roll film 100 is constructed in such a manner that the film 103 which is wound around a spool 102 is stored in a cartridge case 101, which is substantially cylindrical. A light-shielding lid 104 is provided at one end of the cartridge case 101. The film 103 is completely stored in the cartridge case 101 when the roll film 100 has not loaded in the camera or after the roll film 100 has been taken out from the camera, and the light-shielding lid 104 protects the film 103 from external light.
A data disk 105 is provided at a side end of the cartridge case 101, and the data disk 105 rotates in association with the spool 102. A bar code is printed on the exterior face of the data disk 105, and the bar code indicates the type and sensitivity of the film 103, the number of frames to be exposed, etc.
Apertures which are shaped like a circle, a square, a cross and a semicircle are formed on the other side end of the cartridge case 101. A sectorial white plate (not shown) is provided at the back of these apertures, and the white plate rotates in association with the spool 102. One of the circle, the square, the cross and the semicircle is displayed in white according to a position where the white plate stops. The display of the circle in white indicates that the film in the cartridge case 101 is unexposed; the display of the square in white indicates that the film has already been developed; the display of the cross indicates that the film has already been exposed but undeveloped; and the display of the semicircle in white indicates that the film has some unexposed frames remaining. The display in white is called VEI (visual exposure index), and the index is seen with eyes from the outside to confirm the status of the film used.
The film 103 is constructed in such a way that a surface 103F of the film base is coated with a silver salt photosensitive layer and the reverse side 103R of the film is coated with a magnetic recording layer. Multiple perforations 121 are formed at the edge of the film 103 to specify the range of each frame 120. The photographing information such as the type of a light source for photographing and a focal length, and the information such as the title of the photograph used as a message to a user can be magnetically recorded in magnetic record areas 124, 125 at the upper and lower end of each frame.
When the cartridge film is loaded in the camera, an optical reading mechanism in the camera reads information indicated with the bar code on the data disk 105, and detects the position of the white plate, thereby automatically recognizing the information relating to the film and the used status of the film. In the case of the cartridge film with no exposed film or with some unexposed frame remaining, the light-shielding lid 104 is opened and the spool 102 is rotated in a predetermined direction, so that the film 103 can feed to the first unexposed frame.
After all frames on the film 103 are exposed, a rewind mechanism in the camera takes up the film 103 into the cartridge case 101, and closes the light-shielding lid 104. Further, the white plate, which is fixed on the spool 102, is stopped in a manner to face the cross-shaped aperture, thereby displaying the cross in white to indicate that the film has already been exposed.
If the film is forcibly rewound during photographing with some unexposed frames remaining, the rewind mechanism in the camera takes up the film 103 into the cartridge case 101, and closes the light-shielding lid 104. Further, the white plate, which is fixed on the spool 102, is stopped in a manner to face the semicircular aperture, thereby displaying the semicircle in white to indicate that the film has some unexposed frames remaining.
On the other hand, if the loaded cartridge contains the film on which all frames are exposed or developed, the process is executed to prevent the automatic feeding or the like because photographing is impossible.
According to the above-described camera, the film may be forcibly rewound in a state where there are some unexposed frames remaining on the film, and the film cartridge may be taken out of the camera (hereinafter this film cartridge, which contains the film being partially exposed, is referred to as xe2x80x9ca partial cartridgexe2x80x9d). When the partial cartridge, which contains the photographic film with one or more of exposed frames and one or more of unexposed frames, is loaded again in the camera, the information in the magnetic recording layer is read via a magnetic head in the camera, and the film feeds to an area with no magnetic information recorded. Thereby, the photographing can be performed from an unexposed frame.
The magnetic recording layer formed on the photographic film has a low magnetic density. Moreover, the base thereof is harder than a conventional magnetic tape, and thus a head touch easily becomes unstable. Hence, a special magnetic head only for reading is provided in which the number of turns of the coil is increased so as to exactly read the information.
In a magnetic head (a regenerating head) in a conventional magnetic regenerating unit for a camera, which regenerates the magnetic information from the magnetic recording layer on the photographic film, the number of turns of the coil wound around the core is approximately 1500. That is because S/N is lowered if the number of turns is small, and thus the magnetic information is difficult to read.
On the other hand, a magnetic head (a recording head) which records the magnetic information in the magnetic recording layer on the photographic film cannot be driven if the number of turns is large. For this reason, the number of turns of the coil is usually between 80 and 100. Thus, a regenerating head and a recording head are provided independently of one another, or a recording coil and a regenerating coil are wound around a core.
FIG. 33 illustrates an example of a conventional magnetic head driver. The magnetic head driver 150 is driven by electricity supplied from a power source VB, and a lithium battery, which is used as a power source for the camera as a whole, is used as the power source VB. A magnetic head 152 is driven by bridge-connected switching transistors 154, 155, 156, 157, and ON/OFF of which are controlled by control transistors 160, 161. The control transistors 160, 161 are turned on and off, respectively, by switching signals (a clock pulse and a data pulse) which oppositely switch the first port P1 and the second port P2 onto a high (H) level and a low (L) level.
After the start of the magnetic recording, if the port P1 becomes the L level and the port P2 becomes the H level according to the clock pulse and the data pulse from a microcomputer, the control transistor 160 is turned off and the control transistor 161 is turned on. Thereby, the switching transistors 154, 156 are turned off, and the switching transistors 155, 157 are turned on. Thus, the recording current IH flows from the right to the left in the drawing through a coil 152a, which composes the magnetic head 152. Thereby, the magnetic head 152 generates a magnetic field in which the magnetic flux turns in the film feed direction, and a magnetized area (xe2x80x9cN magnetized areaxe2x80x9d) in which the magnetic flux turns in the film feed direction is recorded in the magnetic recording layer. On the other hand, when the port P1 becomes the H level and the port P2 becomes the L level, the control transistor 160 is turned on and the control transistor 161 is turned off. Thereby, the switching transistors 154, 156 are turned on, and the switching transistors 155, 157 are turned off. The recording current flows through the coil 152a in the reverse direction, and the magnetic head 152 generates a magnetic field such that the magnetic flux turns in a direction opposite to the film feed direction, and a magnetized area (xe2x80x9cS magnetized areaxe2x80x9d) in which the magnetic flux is turns in the direction opposite to the film feed direction is recorded in the magnetic recording layer.
The above-described conventional magnetic recording and regenerating unit, however, employs a sensitive and precise regenerating magnetic head in order to read the information recorded in the magnetic recording layer, and this magnetic head is large and expensive. Moreover, since the regenerating magnetic head is provided independently of the recording magnetic head, or the recording and regenerating head uses two coils wound on a core for recording and regenerating, the magnetic head(s) is large and a driver circuit, etc. connected to the magnetic head has the complicated structure. For this reason, the cost is increased, and the camera cannot be compact and lightweight. Since the number of turns of the coil is large, the magnetic head (the regenerating head) in the conventional magnetic regenerating unit for the camera is large and expensive. Due to the deference in the number of turns of the coil in the recording head and the regenerating head, it is impossible to combine them as one magnetic head.
Furthermore, the above-mentioned magnetic head reads the magnetic information while the film is feeding, and thus the noise of the film feed motor easily overlaps with the information. In particular, since the recently-developed cameras are required to be compact, and the motor is arranged close to the magnetic head, the errors easily take place in the process of reading the magnetic information.
If the conventional magnetic head driver is used as shown in FIG. 33, and when all the switching transistors 154, 155, 156, 157 are turned off on completion of recording the last xe2x80x9cS magnetized areaxe2x80x9d, a closed circuit including the magnetic head 152 becomes unstable, and an oscillating current flows through the coil 152a due to the effects of inductance and capacitance within the magnetic head driver. For this reason, there is a problem in that the improper magnetic information is recorded after recording of the last xe2x80x9cS magnetized areaxe2x80x9d because of the oscillating current. To solve this problem, a method has been proposed in which all the transistors 154, 155, 156, 157 are turned on to short-circuit the coil 152a after recording of the last magnetic data (Japanese Patent Application No. 7-128234). This method is effective in a magnetic head driver only for recording, which can have high resistance 164, 165, but is not suitable for a magnetic head driver which is used for both recording and regenerating and has to have small resistance 164, 165 because of the small number of turns of the coil 152a. 
On the other hand, there are well known a four-terminal magnetic head in which the recording coil and the regenerating coil are wound on a core, a three-terminal magnetic head in which the regenerating coil includes the recording coil, and the like. In the magnetic head which is constructed in this manner, the number of turns of the regenerating coil is usually dozens of times as many as the recording coil. When the recording current flows through the recording coil with the drive power of approximately 3 V, an induced current flows through the regenerating coil and a high induced voltage of several dozens V is generated between the ends of the regenerating coil. If the high voltage is directly applied to the amplification circuit for regeneration, elements composing the amplification circuit such as an operational amplifier are broken.
If a protection circuit is provided at the input stage of the amplification circuit for regeneration, or a switch, etc. for electrically cutting off the regenerating amplification circuit from the magnetic head is provided in order to eliminate the above-described disadvantages, the great noise overlaps with the regenerated signal, and the cost is increased.
Furthermore, if the partial cartridge is loaded in the camera, whether a frame is exposed or unexposed must be determined, and the photographic film must be fed to the first unexposed frame, thus requiring much electricity to prepare for photographing. In particular, if whether a frame is exposed or unexposed is determined according to the magnetic information recorded in the magnetic recording layer on the photographic film, the photographic film must be fed at a proper speed. If, for example, the film feed speed changes due to the exhaustion of the battery in the camera, whether a frame is exposed or unexposed cannot be determined, and thus it is impossible to prepare for photographing of the partial cartridge.
It is an object of the present invention to provide a low-noise and low-priced magnetic recording and regenerating unit for photographic film which uses a single magnetic head for both recording and regenerating consisting of a single coil wound around a single core, and which is able to use a recording circuit and a regenerating circuit in the stable condition without effects of mutual noise, and which is able to prevent the breaking of an operational amplifier of the amplification circuit during recording, and a camera which is provided with the magnetic recording and regenerating unit.
It is another object of the present invention to provide a compact camera which is able to effectively eliminate the noise of a motor and correctly determine whether any magnetic information is recorded or not and feed the film to the position of an unexposed frame.
It is yet another object of the present invention to provide a magnetic recording and regenerating unit for photographic film which decreases the number of turns of a coil in a regenerating magnetic head so as to make the magnetic head smaller and less expensive and read all the necessary information, and which may be used as a magnetic head for recording, and a camera which is provided with the magnetic recording and regenerating unit.
To achieve the above-mentioned objects, a camera of the present invention which loads therein a film cartridge containing photographic film coated with a magnetic recording layer, has film feed means for feeding the photographic film from the loaded film cartridge with a motor, determines whether the loaded film cartridge is a partial cartridge, containing a photographic film having an exposed frame and an unexposed frame, or not, and feeds the photographic film from the loaded film cartridge up to a first unexposed frame if determining that the loaded film cartridge is the partial cartridge; the camera comprises: a magnetic recording means for recording magnetic information in a magnetic record area on the magnetic recording layer corresponding to an exposed frame during one-frame feeding in every photographing; and a magnetic regenerating means being unexposed frame detecting means for detecting the first unexposed frame according to whether magnetic information is recorded in a magnetic record area for each frame on the photographic film, if determining that the loaded film cartridge is the partial cartridge, the magnetic regenerating means comprising a magnetic head for contacting the magnetic recording layer while the photographic film is feeding, the magnetic head including a coil wound on a core; an amplification circuit for amplifying signal voltage generated between terminals of the coil; a smoothing circuit for smoothing signals output from the amplification circuit and outputting the smoothed signals; and a magnetic information detecting means for detecting whether any magnetic information is recorded in the magnetic record area for each frame on the photographic film by determining a voltage level of the signals output from the smoothing circuit and comparing the determined voltage level with a reference level.
According to the present invention, the amplification circuit amplifies the signal voltage generated at ends of the coil in the magnetic head, and then the smoothing circuit smoothes the signal voltage. Then, the voltage level of the smoothed signal is read so as to determine whether any magnetic information is recorded or not. The signal is smoothed without accurately reproducing the information recorded in the magnetic recording layer from the signal obtained via the magnetic head, so that the number of turns of the coil in the magnetic head can be small, and hence the camera can be compact and low-priced. The smoothing circuit eliminates the signals at plus or minus side which are overlapped with AC components of the noise from the motor of the film feed means, and picks out signals only at the other side which are not effected by the noise, thereby correctly reading the voltage level. Moreover, by smoothing the signals from the magnetic head, there is no necessity to raise the sampling frequency which specifies the timing for reading the voltage level.
A low-pass filter is provided next to the smoothing circuit, and eliminates the noise caused by a change in a speed at which the film feed means feeds the film, thereby correctly reading the voltage level.
According to another embodiment of the present invention, the camera of the present invention further comprises a film position recognition means for recognizing a position on the photographic film fed by the film feed means with respect to the magnetic head, and characterized in that the film position recognition means recognizes an area in proximity of the center of each frame on the photographic film where there is a high possibility that some magnetic information is recorded if magnetic information is recorded, and the magnetic information detecting means performs the detection only for the recognized area. Since there is some possibilities that no magnetic information is recorded at front and back ends of the magnetic record area for each frame, the regenerated signals are read from the area in proximity of the center where there is a high possibility that some magnetic information is recorded, so that whether any magnetic information is recorded or not can be determined without fail.
According to yet another embodiment of the present invention, a magnetic recording and regenerating unit for photographic film, which has film feed means for feeding photographic film coated with a magnetic recording layer with a motor and has a magnetic recording function of recording magnetic information in the magnetic recording layer while the photographic film is feeding and a magnetic regenerating function of reading magnetic information recorded in the magnetic recording layer, the magnetic recording and regenerating unit comprises: a magnetic head for accessing to the magnetic recording layer while the photographic film is feeding, the magnetic head including a coil wound around a core; a recording circuit for supplying recording current to the coil during recording, and an amplification circuit for amplifying signal voltage generated at ends of the coil during regenerating and thereby outputting an regenerated signal, the recording circuit and the amplification circuit being connected to the ends of the coil in parallel; a reference voltage apply means for applying reference voltage to the amplification circuit only during regenerating, the reference voltage apply means cutting off the reference voltage from the amplification circuit during a period except for regenerating; a driving power supply means for supplying driving power to the amplification circuit during regenerating and recording; and the magnetic recording and regenerating unit is characterized in that, during recording, the amplification circuit functions as a comparator to protect the amplification circuit from input of signal voltage during recording.
According to the present invention, the single magnetic head in which the single coil is wound around the single core is used for both recording and regenerating, and the recording circuit and the amplification circuit for regeneration are directly connected in parallel to the ends of the coil. During regenerating, the drive power and the reference voltage are supplied to an operational amplifier of the amplification circuit, and the amplification circuit functions as the amplifier for regenerated signals. During recording, only the drive power is supplied to the amplification circuit, and the reference voltage is shut off. Thus, during recording, the amplification circuit functions as the comparator. If the signal voltage, which is applied to the ends of the magnetic head during recording, is input to the amplification circuit, the amplification circuit is not broken. There is no necessity to provide the protection circuit, etc., which can be a source of noise, in the input stage of the amplification circuit. Thus, the noise and cost can be reduced.
According to another embodiment of the present invention, a magnetic regenerating unit for a camera, which feeds photographic film coated with a magnetic recording layer and regenerates magnetic information from the magnetic recording layer on the photographic film; the magnetic regenerating unit for the camera comprises: a magnetic head for accessing to the magnetic recording layer while the photographic film is feeding, the magnetic head including a coil wound around a core, a number of turns of the coil being determined so as to output a regenerated waveform which does not enable reading of the magnetic information but permits determination of whether any magnetic information is recorded or not; and a determination means for determining whether any magnetic information is recorded or not in a magnetic record area for each frame on the photographic film based on voltage signals generated at ends of the coil.
According to another embodiment of the prevent invention, a camera which loads therein a film cartridge containing photographic film coated with a magnetic recording layer, has film feed means for feeding the photographic film from the loaded film cartridge with a motor, determines whether the loaded film cartridge is a partial cartridge, containing a photographic film having an exposed frame and an unexposed frame, or not, and feeds the photographic film from the loaded film cartridge up to a first unexposed frame if determining that the loaded film cartridge is the partial cartridge; the camera comprises: a magnetic recording means for recording magnetic information in a magnetic record area on the magnetic recording layer corresponding to an exposed frame during one-frame feeding in every photographing; and an unexposed frame detecting means for detecting the first unexposed frame according to whether magnetic information is recorded in a magnetic record area for each frame on the photographic film, the unexposed frame detecting means comprising a magnetic head for accessing to the magnetic recording layer while the photographic film is feeding, the magnetic head including a coil wound around a core, a number of turns of the coil being determined so as to output a regenerated waveform which does not enable reading of the magnetic information but permits determination of whether any magnetic information is recorded or not; and a determination means for determining whether any magnetic information is recorded or not in a magnetic record area for each frame on the photographic film based on voltage signals generated at ends of the coil.
That is, the magnetic recording and regenerating unit for the photographic film is used when the partial cartridge is loaded again in the camera. The magnetic recording and regenerating unit reads the magnetic information, which are recorded in the magnetic record area for each frame on the photographic film, in order to detect the frame which has no magnetic information (unexposed frame). Thus, the regenerated signals are not needed for the purpose of perfectly reading the magnetic information. Hence, the number of turns of the coil in the magnetic head can be smaller so that the magnetic head can output the regenerated waveform to determine whether any magnetic information is recorded or not, so in this case the magnetic head can be compact and low-priced. The number of turns of the coil is also determined so that the magnetic head can be used for recording the magnetic information.